1. Field of the Invention
This invention relates to drill guides and more particularly to a drill guide assembly releasably attachable to a portable power drill for accurately positioning and guiding the drill relative to a workpiece.
2. Description of the Prior Art
It is extremely difficult to maintain a conventional hand-held portable electric drill in the precise orientation desired during a drilling operation due in part to the lack of symmetry of the drill structure, and in part to the fact that such devices do not include any convenient way of sighting along or parallel to the drill axis. For example, when it is desired to drill a hole normal to a flat surface with such a tool, it is normally necessary to try to visually align the relatively short drill bit perpendicular to the workpiece by sighting the drill bit from various positions around the drill and thereafter to try to maintain the assembly in the sighted position while applying pressure to the off-set pistol grip handle of the housing. Difficulty is also encountered in drilling holes perpendicular to a cylindrical surface or to a compound curved surface, and in drilling holes precisely on the centerline and perpendicular to relatively narrow flat surfaces.
In an effort to overcome the difficulties in using hand-held power drills, numerous prior art devices have been developed to orient the drill relative to the surface of the workpiece. However, these prior art devices have not always been successful, and generally have not met wide-spread acceptance for various reasons. For example, many of the prior art devices have been designed for use only with specific drill structures, or have required some modifications of the drill structure for attachment thereto, and therefore have not been readily useable with the numerous existing makes and models of drills. Further, some prior art devices have been prohibitively expensive for use as an attachment for a relatively inexpensive drill of the type frequently purchased by homeowners or small shops.
It is the primary object of the present invention, therefore, to provide a drill guide which is quickly and easily mounted on most conventional, commercial hand-held power drills, and which will reliably and accurately support the drill for drilling holes normal to a workpiece surface.
Another object of the invention is to provide a lightweight, reliable, easy-to-use, and inexpensive drill guide which may be used with commercial hand drills without modification of the drill structure.